Generally, rubber modified aromatic vinyl copolymer resins can have good mold processability, impact strength, and appearance and have accordingly been widely used in the production of many electric or electronic goods. When a rubber modified aromatic vinyl copolymer resin is used in the production of heat-emitting products, the resin should further have flame retardancy.
A halogen-containing compound and an antimony-containing compound can be added to a rubber modified aromatic vinyl copolymer resin to give the resin good flame-retardant properties. However, the halogen-containing flame retardant is potentially harmful. Accordingly, a major concern in this field is to develop a flame retardant-rubber modified aromatic vinyl copolymer resin without a halogen-containing compound.
It is well known to employ a phosphorous, silicon, boron, or nitrogen compound as a halogen-free flame retardant for a resin composition. However, such compounds cannot impart sufficient flame retardancy.
Journal of Polymer (Elsevier Science, 1975, vol. 16, pp. 615-620) discloses that rubber modified styrene-containing resin has a low Limiting Oxygen Index (LOI), because it does not form char during thermogravimetric analysis (TGA) and combustion. Halogen-containing compounds can readily impart a desired degree of flame-retardancy, regardless of the kind of resin. It is difficult, however, to provide rubber modified styrene-containing resins which do not form char with sufficient flame retardancy using only phosphorous- or nitrogen-flame retardants, because these non-halogenated flame retardants typically act on a solid phase.
In order to solve the above problems, U.S. Pat. Nos. 5,061,745; 5,204,394; and 5,674,924 disclose adding a phosphate ester compound and a polycarbonate to a rubber modified aromatic vinyl copolymer resin to impart flame retardancy. However, a relatively high amount of polycarbonate is required to obtain sufficient flame retardancy.